I can't speak for Adobe, but what I can say is I think I first heard that the allowed paths template property was being deprecated back in 5.2.1. I'd say that's been the message for going on 4 or 5 years now but Adobe has yet to actually remove support for it. I have continued to use it on my implementations and will probably continue to do so until it's actually removed from the product. It allows you control you template availability effectively based on only template configuration without dependencies for properties set on content nodes.